The jurors picked by the end of the day's proceedings came from a pool of more than 220 prospective jurors, 40 of whom still awaited individual questioning, the Pittsburgh Post-Gazette reported.
WHTM-TV reported the jurors selected so far included five men and four women. Twelve jurors and four alternates will be picked.
The Harrisburg TV station said Senior Judge John Cleland underscored the jury's responsibility.
"They have justice in their hands," he said. "They are the protectors of democracy. The government cannot imprison anyone unless they say it's OK."
Sandusky, who is charged with 52 counts of sexually abusing 10 boys over 15 years, was present for the questioning and selection of the jury, the Centre Daily Times of State College, Pa., reported.
Potential jurors received instructions from Cleland before attorneys begin interviewing them at the courthouse in Bellefonte, about 10 miles northeast of State College, Penn State's location.
Twenty potential jurors were sent home after questioning Tuesday. Among those not selected were a mother of three young sons who said she didn't think she could be fair, a man who said he knew a party in the case and a man who volunteered with the children's charity Sandusky founded, the Post-Gazette reported.
Opening statements in the trial are scheduled for Monday.
The jury selection started a day after Pennsylvania's top court denied Sandusky's 11th-hour bid to delay the start of his child sex-abuse trial.
The state's Supreme Court ruled against an "Emergency Application for Extraordinary Relief" filed by the former Penn State defensive coordinator, who has tried for months to stop, postpone or limit the case.
In a "per curiam" decision reflecting the unanimous but unsigned collective decision of the court's seven justices, the court Monday denied the delay without fuller explanation.
Sandusky lawyer Joseph Amendola had asked for the delay, arguing that two experts -- a jury consultant and a mental health professional -- were not ready; an investigator would be having surgery; two potential defense witnesses would be unavailable because they exercised their Fifth Amendment right to avoid self-incrimination, and the defense did not have enough time to review all the evidence.
Sandusky, arrested Nov. 5, allegedly met the boys he is accused of sexually abusing through the Second Mile children's charity he founded.
Some of the alleged assaults occurred on the Penn State campus.
Sandusky, 68, denies all the allegations.
His arrest engulfed the Penn State football program in scandal and led to the firing of renowned head Coach Joe Paterno for "failure of leadership"
Also ousted was Graham Spanier, Penn State's longtime president.
Mike McQueary, a former Penn State quarterback who became an assistant coach, testified before a grand jury he had told Paterno about an alleged sexual-abuse incident he witnessed in a Penn State locker room.
Paterno reported it to his superiors but not to police.
Prosecutors have not said whether McQueary will be called to testify.
Paterno -- who led the Penn State Nittany Lions for nearly 46 years and held a record 409 victories by an NCAA Division I football bowl subdivision -- died of lung cancer Jan. 22 at age 85.
In a separate ruling, Cleland said Monday Sandusky's accusers -- several of whom are now adults -- must use their real names when testifying. He also said reporters could not send Twitter messages or blog from the courtroom.
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